Academic or Employer LoR?

[Focus]

Hello all,

I currently intern in a lab at a small school that I am not attending. I have worked with a few of the faculty here for two summers and they have supervised all of my research. A small handful have been kind enough to offer to write me LoR's and I intend to take the two strongest letter writer's up on their offer. 

The primary letter writer is a biologist that I have spent the most time working with; the other is an immunologist that I have been working with only for 1 summer. (I intend to apply to immunology programs.)
I was thinking about having all 3 letter's from this institution, but thought it would be strange, considering that I'm not a student. 
I would like to implement a LoR from my home institution, and need some opinions on who to choose for my third writer.

Currently, I'm choosing between my current boss who runs the school tutoring center (who I have been told writes GLOWING LoR's) and has always been very supportive and encouraging in my grad school pursuits, or two professors. I distinguished myself well in both professor's classes, but.. Professor A is department chair, advisor for a club that I am president of, and in a chemistry (not biological science) field. Professor B is an assistant professor, a professor in my major (biochemistry), that has a more thorough knowledge of my academic performance. Both professors sat in a council and agreed to award me a school scholarship in chemistry/biochemistry (so my assumption is they both like me). 

Am I overthinking this?

Should I do one from each facet of my life? Research, academic, and employment?

If so, which writers would you suggest?

 

Thanks!

[rising_star]

For PhD applications, all of your applications should be about your research or academics. I would go with the biologist that you've done research with plus the two professors at your home institution. A letter from your boss about your skills as a tutor isn't going to be a factor in your admissions decision.

[TakeruK]

It might just be preference or field, but I would actually go with 2 professors from the other institution (the biologist you worked with and the immunologist your worked with) plus one professor from your current school. From the info given here, I'd choose Prof B from your current school but maybe Prof A is just as good if I knew the whole story.

 

The reason for this ranking is that from my point of view (physical science), research LORs are the most important, and that for top students, it's pretty common for them to go to other institutions to do summer research. So, it's not strange at all if your LORs are not from your institution because you did research at other places. Since it only sounds like you have 2 research LORs, you should definitely pick those two and your third LOR should be a professor from your own school that knows you the best (sounds like Prof B to me here). But if you did another internship or other research position then you should pick that as your third letter.